Variable Range Hopping Transport Probed by DNA Sensing in Vertical Graphene and Nanocrystalline Graphite BioFETs

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Biosensing performance in graphene field-effect transistors (BioFETs) is often attributed to surface chemistry.
• The underlying charge transport mechanisms influencing BioFET sensing remain poorly understood.

Purpose of the Study:

• To establish a direct correlation between disorder-driven transport and biosensing transduction in vertical graphene (VG) and nanocrystalline graphite (NCG) FETs.
• To develop a unified framework for understanding graphene BioFET sensing mechanisms.

Main Methods:

• Temperature-dependent electrical characterization (15-500 K) of VG and NCG FETs.
• Analysis of transport regimes including three-dimensional Mott variable-range hopping (VRH) and Arrhenius-type conduction.
• Surface functionalization with DNA probes and subsequent hybridization experiments.

Main Results:

• VG and NCG FETs exhibit distinct disorder landscapes and transport mechanisms (localized vs. percolative).
• Biosensing response is mechanistically interpretable within a VRH-transconductance framework.
• NCG transduces binding via charge transfer/hopping perturbation; VG responds via electrostatic reorganization.

Conclusions:

• Disorder-driven transport significantly impacts graphene BioFET sensing performance.
• A unified VRH-transconductance-sensing framework provides a physical basis for designing next-generation graphene BioFETs.